The Swedish patent application WO/78.03046-7 (U.S. patent application Ser. No. 779 152, filed Mar. 18, 1977 and now U.S. Pat. No. 4,135,178 which is the parent of U.S. patent application Ser. No. 41,551, filed May 23, 1979, now U.S. Pat. No. 4,317,367) contains a description of different embodiments of a device similar to that according to the invention and how the device according to the invention can be applied. The idea behind the present invention is to produce such a device, but which is of a simpler type and which can be made by a simpler method of manufacture.
In U.S. patent applications Ser. No. 787,422 filed Apr. 14, 1977, now U.S. Pat. No. 4,200,970, and Ser. No. 879,193, filed Feb. 21, 1978) different trimming procedures for devices similar to that according to the invention are described. It should be possible to apply similar trimming procedures for the trimming of the device in accordance with the invention.